An operation input unit represented by a kind of a keyboard in a personal computer has been placed and used in a position in which a user uses it up until now.
However, although using the keyboard being placed on a desk is convenient during use, while the personal computer is not used, a space on the desk capable of being most conveniently used is wastefully occupied by the keyboard.
Therefore, a technology is proposed in which an entire desk is made of a touch panel, while the keyboard is displayed only when required, and the display is erased when no longer required, thereby allowing the space in which the keyboard has been displayed to be used for other work (see PTL 1).